This invention relates to a piston-type fluid suspension system and more particularly to a piston assembly having a bypass valve for selectively adjusting the damping characteristics of the shock absorber both during compression and rebound strokes of the shock absorber piston.
Various piston-type fluid shock absorbers have included apparatus for adjusting or controllably varying the shock absorbers, damping characteristics or cushioning effects during compression or rebound of the shock absorber. In prior shock absorbers of this type, various fluid openings have been disposed in, or otherwise associated with, the shock absorber piston or the piston rod, along with means for selectively opening or closing such fluid openings in order to vary the resistance to hydraulic fluid flowing through the piston or piston end piston rod assembly.
Because different driving characteristics depend upon the amount of damping forces the shock absorber provides, it is often desirable to have a shock absorber in which the amount of damping forces generated by the shock absorber is adjustable. Exemplary of a shock absorber for selectively changing the damping characteristics of a shock absorber is U.S. Pat. No. 5,016,908, issued May 21, 1991, "Method and Apparatus for Controlling Shock Absorbers", the disclosure of which is hereby incorporated by reference.
Further, the greater the degree to which the flow of damping fluid within the working chamber is restricted by a piston assembly, the greater the damping forces which are provided by the shock absorber Accordingly, a "soft" compression and rebound stroke is produced when the flow of damping fluid is relatively unrestricted and a "firm" compression and rebound stroke is produced when the flow of damping fluid is restricted.
An object of the shock absorber of this application is provision of a method and apparatus for controlling shock absorbers in which the amount of damping fluid flowing between the upper and lower portions of the working chamber can be controlled with a relatively high degree of accuracy and speed. Advantageously, such apparatus when adjusted would provide enhanced road holding and handling by rapidly changing between "firm" and "soft" rebound and compression conditions.
Another object of this invention is simplification of the piston assembly by reducing both the number and complexity of the components thereof needed to control the damping forces. Advantageously, a by-pass valve is driven by a ported plunger, from a first position, to produce a soft compression stroke and a firm rebound stroke, and to a second position, to produce a firm-compression stroke and a soft rebound stroke. The improved piston assembly enhances the road handling ability and/or road holding ability of the vehicle by controlling the damping forces of the shock absorber.
Another object of the invention is to provide a new and improved piston assembly for a shock absorber that employs a "floating" piston within the piston of an existing shock absorber to control the damping flow conditions. Advantageously the floating piston is a relatively uncomplicated design, economical to manufacture, and is adaptable to a wide variety of adjustment applications.
Another object of the present invention is to provide a method of apparatus for controlling shock absorbers in which the occurrence of a compression or rebound stroke may be determined by measuring the pressure differential between the damping fluid in the upper and lower portions of the working chamber (i.e., the pressure difference across the piston of the shock absorber).
Yet another object of the present invention is to provide a shock absorber whose damping characteristics can be easily and conveniently controlled from a remote or external position relative to the shock absorber and which is adaptable to a wide variety of adjustment actuation applications.
To achieve the above-mentioned objects, a controllable fluid shock absorber assembly includes a cylinder defining a fluid pressure chamber, a piston rod slidably movable within the chamber, and a piston secured to the piston rod for movement therewith. The piston rod extends outwardly from the chamber, is centrally bored, and has fluid openings to pass fluid. The piston comprises a cylindrical piston body that divides the pressure chamber into an upper rebound and a lower compression chamber. In accordance with the preferred embodiments of the present invention, the piston body has a fluid reserve chamber therewithin which receives a "floating" piston, restricted first flow passages which operate to pass fluid between the upper and lower chambers during respective compression and rebound strokes, second flow passages which operate to pass fluid between the upper and lower chambers via internal pilot ports and the fluid reserve chamber, and third flow passages or openings to communicate damping fluid between the chamber and the second passages. The floating piston divides the fluid reserve chamber into upper and lower pressure chambers and includes an internal chamber that defines a passageway to pass fluid from the second passages, through the third flow passages, through the internal chamber of the piston and through the bore of the piston rod. The floating piston is controlled by operating pressures found inside the chamber which are routed by a solenoid valve that controls the flow of damping fluid between the upper and lower chambers of the working chamber during compression and rebound of the piston. An external control unit electrically controls a solenoid valve to move the respective openings of a plunger between a first and second position to control the flow of damping fluid through first and second flow paths, respectively, relative to the first and second chamber portions.
Advantageously, the floating piston operates to efficiently and rapidly change the ride characteristics of the shock absorber assembly. Further, sensor means used in connection externally with the shock absorber change the ride characteristics of a car depending upon the user's desires.
Other objects, advantages and features of the present invention will become apparent to one skilled in the art upon reading the following description and dependent claims, taken in conjunction with the following drawings.